1. Technical Field
The present invention relates to a percussion driver drill comprising a vibrator mechanism for imparting an axial vibration to a spindle, and a clutch mechanism for setting a maximum torque of the spindle.
2. Background Art
A percussion driver drill is implemented with selectable modes which include a drill mode in which a spindle protruding frontward from a housing is caused to make a rotatory motion, a percussion drill mode in which an axial vibratory motion is additionally imparted to the spindle, and a clutch mode in which a transmission of torque is interrupted when the torque gets beyond a predetermined maximum torque. Among these modes, the percussion drill mode is implemented, as described in Japanese Unexamined Patent Application Publication No. 2005-193361 (corresponding US Patent Application is published under US 2005/0150669 A1), with a vibration mechanism which includes a first cam fixed to the spindle, a second cam disposed rearwardly of the first cam and configured to be rotatable and movable in the front-rear direction, a vibration switch lever (slider) configured to be engageable with the second cam, and a mode change ring operable to cause the vibration switch lever to engage with and disengage from the second cam. In operation, the mode change ring is operated to make a rotatory motion, which causes the vibration switch lever to engage with the second cam to thereby restrict the rotation of the second cam, so that a vibratory motion is obtained. On the other hand, the clutch mode is implemented with a clutch mechanism which includes an internal gear rotatably provided at a final stage of a planetary gear speed reduction mechanism which lowers the output rotational speed of the motor, a coil spring provided to press an engageable member such as a ball against the internal gear, and a change ring configured to cause a holder which receives the coil spring to screw forward to thereby change an axial length of the coil spring. In operation, the change ring is operated to make a rotatory motion to thereby set a pressing force of the coil spring, so that when a torque beyond the thus-set pressing force of the coil spring is applied, the internal gear runs idle to interrupt the transmission of the torque.
In this percussion driver drill as described above, a switch member (vibration switch lever) and an operating member (mode change ring) of the vibration mechanism are disposed radially inside and outside, respectively, with the coil spring of the clutch mechanism interposed therebetween. Therefore, the clutch mechanism and vibration mechanism should be arranged in positions shifted in the axial direction from each other in order to avoid interference with the coil spring. As a result, the entire length of the tool in the axial direction is increased accordingly, which would become an obstacle to miniaturization of the percussion driver drill.
With this in view, it would be desirable to provide a percussion driver drill in which both of the vibration mechanism and the clutch mechanism are provided while the length in the axial direction is shortened to achieve a substantial miniaturization of the percussion driver drill.
The present invention has been made in an attempt to eliminate the above disadvantage, and illustrative, non-limiting embodiments of the present invention overcome the above disadvantage and other disadvantages not described above.